1. Field
Embodiments of the present disclosure relate to control of an internal combustion engine during transient events using ionization sensing.
2. Background
Transient events may occur in response to a change in driver demand, such as an increase or decrease in accelerator pedal position, and/or in response to changing engine or ambient conditions, such as during engine warm-up, for example. In port-injected engine applications, evaporation rate of the fuel puddle in the intake port is affected by differences in intake manifold filling and intake manifold pressure during increases and decreases in accelerator pedal/throttle valve positions, often referred to as tip-ins and tip-outs, respectively. Uncompensated air/fuel control would result in leaner than desired air/fuel ratios during tip-ins, and richer than desired air/fuel ratios during tip-outs. As such, the engine control strategy may increase fuel delivery to the engine for a period of time based on an empirically determined time constant established during engine development for the period of increased torque demand during a tip-in. Similarly, another empirically determined time constant may be applied by the engine control strategy to decrease fuel delivery for a period of time during decreased torque demand during a tip-out. This transient fuel compensation strategy is often performed in open loop fashion and relies on significant development resources related to data collection at various operating conditions for accurate calibration.
The desired transient fuel increase/decrease may depend on a number of factors, such as fuel type, air charge temperature, engine coolant temperature, air flow, manifold pressure, engine deposits, etc. However, the number of operating variables and the number of values for each variable actually implemented in the control strategy are generally limited by the available memory for the controller and the labor-intensive development task of determining suitable values under the selected operating conditions for a wide variety of engine applications and implementations. Suitable calibrations for engine warm-up are particularly difficult to develop due to the limited period of time at the various engine coolant, engine speed, and engine load operating conditions during representative warm-up cycles. Furthermore, fuels with various distillation characteristics can result in varying evaporation rates where less of the injected fuel is available for combustion within the combustion chamber. The resulting open loop calibration strategy can not adjust for fuel properties without the addition of a costly sensor, or by inferring the properties from other sensors.